Traditionally, walls constructed using block required mortar joints between courses of blocks and between blocks within a course. One advantage of mortar joints is that they produce a wall having a somewhat aesthetically pleasing, decorative appearance. Specifically, the mortar joints reveal the block pattern (i.e. bond) of the wall, which is often desirable for architectural purposes. On the other hand, the use of mortar joints presents several disadvantages. For one, structures with mortar joints are expensive, in part due to the cost of the mortar material and the labor cost involved in preparing (i.e. mixing) the mortar at the construction site.
In addition to the cost of the mortar, construction using mortar joints tends to be expensive because it is time consuming to apply the mortar and then level and align each block. These construction steps are usually performed by a skilled mason who typically garners a relatively high hourly wage. Another disadvantage associated with a mortar joints is that mortar joints are relatively weak as compared to the remainder of the structure. This is partially due to the fact that the mortar is prepared at the construction site, often under non-optimal conditions. Unlike the mortar joints, concrete blocks are generally strong because they are typically pressure molded at a factory in a controlled environment. Moreover, block walls with weak mortar joints are particularly susceptible to damage if the wall is shaken, for example, during a moderate to strong earthquake.
Mortarless joint construction block systems offer an alternative to the labor intensive process used to prepare structures with mortar joints. These mortarless joint systems often rely on specific features that are formed on the blocks to interlock the blocks and hold the resulting wall together. Once interlocked, a mortar mix can be pumped or poured into holes in the blocks in a relatively non labor-intensive process to produce a wall having excellent structural integrity. In some cases the blocks can be designed for construction of walls that are reinforced using re-bar.
Once the wall is erected, it is often covered with plaster to enhance its appearance. For plaster covered walls, the plaster functions to prevent water from entering the joint between blocks where the water can damage the structural integrity of the wall. On the other hand, it is somewhat costly and time consuming to plaster the entire outside surface of a wall. Accordingly, it is sometimes desirable to use a wall without plaster on some or all of the wall's outside surfaces. However, currently available mortarless joint systems do not effectively prevent water from seeping into the joints between blocks, and accordingly, these system require a surface coating such as plaster to ensure the structural integrity of the block wall is maintained.
Another important factor that must be considered in the design of interlocking block construction systems is their resistance to earthquakes. Strong earthquakes and some moderately strong earthquakes can shake a block wall causing rigid joints between blocks to fracture. Typical interlocking block systems do not allow for any movement at the joints between adjacent blocks. Because of this rigid structure, walls constructed using these systems tend to fail when exposed to moderately strong seismic activity. On the other hand, the present invention recognizes that some movement between adjacent blocks (on the same course and between courses) can prevent cracking during seismic activity. In particular, the present invention recognizes that hinge-type movement between adjacent blocks can allow a wall to withstand relatively strong seismic activity without damage.
In light of the above, it is an object of the present invention to provide concrete block construction systems having interlocking, self-aligning blocks. It is another object of the present invention to provide block construction systems having mortarless joints which are designed to prevent water from seeping into joints between blocks. It is yet another object of the present invention to provide a block construction system for producing walls that can be used without failure in areas that experience frequent seismic activity. Yet another object of the present invention is to provide a block construction system which is easy to use, relatively simple to implement, and comparatively cost effective.